Refining of mineral oils



Patented Mar. 7, 1944 DEFINING or MINERAL orts Henry C. vPaulsen, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 24, 1941,

Serial No. 390,133 r 6 Claims. (Cl. 196-32) "1y, particularly the relatively high boiling mer- The present invention is concerned with the refining of mineral oils. ticularly relates to an improved process for the The invention more par removal of mercaptan compounds from oils, es-" pecially from petroleum oils boiling in the motor In accordance fuel and. gas oil boiling ranges. with the present process, objectionable mercaptan compounds are removed from oils containing the same utilizing an alkaline solution such as an alkali metal hydroxide solution containing dissolved therein an oxygenated amino compound. The amino compound is characterized by comprising a six member ring structure having an oxygen atom and a nitrogen atom in the ring linkage. When utilizing a treating solution of this character, mercaptan compounds are efiiciently removed in an economical manner. Furthermore, the solution may be readily regenerated for recycling to the treating zone.

It is known in the art to refine oils such as petroleum oils by various procedures in order to produce products of a satisfactory quality. For example, it is known in the art to remove objectionable mercaptan compounds from petroleum oils utilizing a number of operations. One operation comprises treating the mercaptan-containing feed oil with a socalled doctor solution which comprises a sodium hydroxide solution of lead oxide under conditions to convert the mercaptan compounds to soluble alkyl disulfide compounds.

This operation does not reduce the total sulfur content of the oil but merely converts the sulfur compounds into relatively innocuous materials. In an operation of this character, the doctor treated oil containing soluble lead mercaptides is usually treated with free sulfur so as to precipitate the lead as lead sulfide and to form the corresponding oil soluble relatively harmless alkyl disulfides.

One disadvantage of this process for the removal of mercaptans is that considerable care must be exercised with respect to the addition of the free sulfur. If insumcient sulfur be added, all the lead mercaptides are not removed from the oil which results in a product of inferior quality. On the other hand, if an excess of sulfur be added, this excess sulfur remains dissolved in the treated oil which increases its corrosiveness and in many instances necessitates rerunning of the oil. Thus, various suggestions have been made that these objectionable mercaptan compounds be removed from the oil in a manner to completely free or at least considerably lower, the total sulfur content of the treated oil. For example, it has been suggested that the oil be treated with an alkali metal hydroxide solution, such as with a sodium hydroxide solution. However, in order to remove the mercaptan compounds satisfactori- -captan compounds, it is necessary to use a relatively large quantity of the reagent based upon the volume of oil treated. This is particularly the case when treating relatively high boiling oils,

as for example, those oils boiling in the heavy naphtha, heating oil, and gas oil boiling ranges,

' which oils boil in the general range from about 250 F. to about 750 F.

I have now discovered a process by which mercaptan compounds may be efliciently removed from petroleum oils containing the same. My process comprises utilizing a treating solution comprising a alkaline solution and a substance selected from the class of compounds which are characterized by being six member ring compounds and which are further characterized by having a nitrogen atom and an oxygen atom in the ring linkage.

The alkaline treating solution may be any suitable alkaline solution such as metallic carbonate solution, alkali metal or alkaline earth metal hydroxide solutions. It is, however, preferred that the alkaline solution comprise an alkali metal hydroxide solution as, for example, a sodium hydroxide solution or a potassium hydroxide solution.

The organic substance is selected from the class of compounds which are characterized by having the following structural formula:

in which R1, R2, R3, and R4 represent alkyl groups and in which R5 represents hydrogen, an alkyl group, or an oxygenated alkyl group. Suitable organic substances are, for example,'morpholine, O(CH2CH2)2NH, 4 beta ethoxyethyl morpholine, O(CH2CH2)2N CH2CH2OC2H5, and 4 morpholine ethanol, 0(CH2CH2)2N CHzCHzOI-I. I have found that particularly desirable results are secured when morpholine is employed in conjunction with a solution of sodium hydroxide.

The concentration of the respective constituents will vary widely depending upon the oil being treated, the particular alkaline solution being used, and the particular organic substance being employed. In general, it is preferred that the solution comprise from about 10% to orgame agent, preferably from about 40% to 50%, and that the remainder comprise an alkali metal hydroxide solution.

The quantity of treating solution employed per volume of oil being treated likewise will vary considerably depending upon the character and concentration of the mercaptan compounds prescut as well as upon the particular treating reprised potassium hydroxide and morpholine. The results of these operations are as follows:

Treated Treated with 110- Treated with 2 3521 5? with 110- tassium hydrox water soluna hum tassium ide solution of tion oflmorp hydroxide inol'pholine pholine Composition of reagents:

KOH 140 gmsi/liter per cent-- 100 60 60 60 Mor do 40 40 40 60 Operating conditions:

Treating temp F 75 75 75 75 76 TreaL. per cent 10 10 2X10 3X10 l Gasoline inspections:

Mg. mercaptan/100 .mi 36 23 ll 1. 5 36 Mercaptan removal per cent 36 69 96 None Sulfur per cent by weight.- 0. 204 0.190 0. 167 0. 159 Gravity A. P. 50.9 Distillation, Engler- Initial boiling point .F 172 Per cent distilled et 1 Tetrahydro-l, 4-oxazine or diethylenimide oxide.

agent used. In general it is preferred to employ from about to about volumes of a morpholine-sodium hydroxide solution per 100 volumes of oil being treated. The operating conditions may also vary considerably. Temperatures in the general range from about 32 F. to about 140 F. may be employed. It is, however, preferred to employ temperatures in the range from about 40 F. to 80 F. The oil and treating reagent may be contacted by a batch, a semibatch operation, or by a countercurrent treating operation. Usually a continuous countercurrent operation is preferred. The time of contact is also adjusted and regulated so as to secure the desired removal of the objectionable mercaptan compounds. The timeof contact will be a function of the above enumerated factors.

The treated oil and the spent alkaline reagent are separated by suitable means, after which the alkaline solution may be regenerated and recycled to the treating zone. In general, it is preferred to regenerate the Spent alkaline solution by treatme the same with steam under conditions to form the mercaptans which are volatilized and removed overhead. I

In order to illustrate the invention further, the following example is given which should not be construed as limiting the same in any manner whatsoever.

Example Segregated portions 'of a cracked petroleum oil boiling in the motor fuel boiling range were treated in several operations. In one operation a potassium hydroxide was employed while in the other operations the treating solution com- Although any alkali solution may be used, I particularly prefer to employ alkali metal hydroxide sclutions,-especially a sodium hydroxide solution. When utilizing a sodium hydroxide solution, I prefer to use a solution of from about 2 to 10 normal sodium hydroxide solution calculated on the total solution, and to use from about 0.2 to 0.4 volume of sodium hydroxide solution per volume of oil.

What I claim as new and wish to protect by Letters Patent is:

1. Process for the removal of mercaptan compounds from oil which comprises contacting a feed oil containing mercaptan compounds with a treating agent comprising an alkali metal hydroxide solution and morpholine.

2. Process as defined by claim 1 in which said alkali metal hydroxide solution comprises a sodium hydroxide solution.

3. Process as defined by claim 1 in which said alkalimetal hydroxide solution comprises a sodium hydroxide solution and in which the feed oil is treated with from about 0.2 to about 0.4 volume of treating agent per volume of oil.

4. Process for the removal of mercaptan compounds from oil, which comprises contacting a feed oil containing mercaptan compounds with a treating agent comprising an alkali metal hydroxide solution containing about 10% to 60% of morpholine.

alkali metal hydroxide solution is within the limits of about 2 to about 10 normal.

HENRY C. PAULSEN. 

